Water

Question 1

Describe structure of water

Answer 1

1 atom of oxygen bonded contently to 2 atoms of hydrogen.Hydrogen is left with a slightly positive charge as the electrons are pulled away from the hydrogen atom. Oxygen has a greater share of electrons, so is left with a slightly negative charge. Therefore water is a polar molecule as the charges are segregated

Question 2

Property of water- High SHC
Give def

Answer 2

The energy needed to raise the temperature of 1g of a substance by 1°C

Question 3

δ-

Answer 3

delta negative (slightly negative)

Question 4

δ+

Answer 4

delta positive (slightly positive)

Question 5

Property of water- High SHC
Give reason and role (importance)

Answer 5

A large amount of energy needed to increase water temperature because the hydrogen bonds absorb a lot of energy. This means large fluctuation in water temperature do not occur, providing stability for aquatic organisms.

Question 6

Property of water- High latent heat of vaporisation
Give reason and role (importance)

Answer 6

A lot of energy is needed to break the hydrogen bonds between water molecules so that water becomes gaseous. Hydrogen bonds themselves are weak but in high numbers, a lot of energy is needed.
This makes water an excellent coolant as mammals can sweat, exerting heat away. transpiration occurs in plants, carrying heat away. Provides a temp buffer for chemical reactions. Allows proper function for enzymes as they are active in a narrow temp change

Question 7

Property of water- Very cohesive
Give reason and role (importance)

Answer 7

Attraction between water molecules. Water molecules will stick together allowing them to flow and stay as one mass. This allows transpiration as hydrogen bond to the oxygen and stick, allowing water to be drawn up the xylem tubes. This causes surface tension.

Question 8

Property of water- Adhesive
Give reason and role (importance)

Answer 8

Adhesion is the attraction between water molecules have for other polar substances. The combination of adhesion and cohesion allows water to move through xylem and allows capillary action.

Question 9

Property of water- Lower density when solid
Give reason and role (importance)

Answer 9

When water changes state, each water molecule forms 4 hydrogen bonds to other water molecules, making ice less dense than water. This allows ice to float. I
Importance- Ice forms an insulating layer which reduces rate of heat loss. Environment is made more stable for aquatic organisms. Ice also serves as a habitat for animals eg. polar bears

Question 10

Property of water- Good solvent
Give reason and role (importance)

Answer 10

water is polar, so the slightly positive end will be attracted to negative ions. The slightly negative side will be attracted to positive ions. water molecules form a hydration shell around the ion, so they can dissolve.
Importance- enables transportation of molecules in living organisms. Ions can dissolve in water in blood and are important for regulation of PH balance. most chemical reactions take place in a solution

Question 11

Which substances dissolve in water?

Answer 11

ions and polar substances, shown by an OH or SH group.

Question 12

Why is it useful to organisms that water is liquid at room temp

Answer 12

• An effective transport medium
• Habitat for aquatic organisms
  -Medium for chemical reactions

Question 13

What does polar mean

Answer 13

Region of positive and negative charges